Pressure regulating structure for piston pump



PRESSURE REGULATING STRUCTURE FOR PISTON PUMP Filed March 3. 1969 INVENTOR CARL E MALONE 40 \V Q \V iv I If (I 4 v 6 h 2 2 Z; M; w w m 5 m a A M r 4 51 ATTORNEYS United States Patent 3,514,017 PRESSURE REGULATING STRUCTURE FOR PISTON PUMP Carl E. Malone, Fort Lauderdale, Fla., assignor to The AFA Corporation of Florida, Miami, Fla., :1 corporation of Florida Filed Mar. 3, 1969, Ser. No. 803,686 Int. Cl. G01f 11/06 US. Cl. 222-321 Claims ABSTRACT OF THE DISCLOSURE An end-of-stroke pressure release mechanism for a liquid pressurizing pump having a piston reciprocable in a cylinder for pressurizing a body of liquid in the pump chamber of the cylinder. Gradual drop off in pressure as the piston reaches the end of its pumping stroke is prevented by a bypass pressure release passage which connects the pump chamber with a zone of lower pressure when the pump piston has travelled substantially to the end of said stroke. An O-ring seal carried by the piston cooperates with the bypass passage and serves as a valve for opening and closing the passage whereby pump chamber pressure is rapidly'relieved and then the bypass passage is rescaled for the subsequent intake stroke of the piston.

This invention relates to liquid pressurizing devices and in particular to a liquid pressurizing piston pump adapted to force a body of liquid under high pressure to a spray nozzle for developing a spray mist.

In many liquid dispensing devices in which a liquid is pressurized in a pump chamber of a piston-cylinder type pump, and particularly wherein the piston is actuated either manually or by some resilient means such as a spring, there is a noticeable and often rather prolonged pressure drop-off which takes place as the piston reaches the end of its liquid pumping stroke in the cylinder. This condition is particularly noticeable in liquid pumps wherein air is either intentionally or inadvertently mixed with a liquid in the pump chamber or wherein a peculiar configuration of the parts of the dispensing device makes it difficult if not impossible to eliminate all air pockets in the passageways connecting the pump chamber with the liquid dispensing nozzle. Consequently, whenever air is present, due to air being a gas and thus readily compressible as compared to the liquid being dispensed, as the piston approaches the efid of its chamberemptying stroke the hydraulic pressure drops off gradually due to the air bell residual expansion action of the entrapped air creating this prolonged pressure dropotf. This condition is most noticeable when the discharge nozzle is controlled by a discharge valve which is held open as the piston is allowed to complete its pressurizing and/ or delivery stroke.

The aforementioned gradual pressure drop-01f condi tion represents a serious problem in those liquid dispensing devices where constant high hydraulic pressure is important, as where the liquid pump is used to pressurize liquid to be dispensed in the form of a spray mist, i.e., where the liquid is forced through a nozzle with a restricted orifice and the nozzle has some type of mechanical structure to produce, through hydraulic atomization, a fine mist or spray. For example, one such liquid spraying device is that disclosed and claimed in my co-pending application Ser. No. 712,306, filed Mar. 11, 1968 entitled Liquid Spraying Device, which is a continuation of my prior co-pending application Ser. No. 488,454, filed Sept. 28, 1965, now abandoned. Should an air entrapment condition develop in this device, a somewhat 3,514,017 Patented May 26 1970 prolonged pressure drop-off may occur at the end of the emptying stroke of the piston which in turn causes the liquid emerging from the nozzle to change from a high quality fine spray or mist into an annoying weak stream or dribble.

An object of the present invention is to provide a simple and inexpensive pressure release mechanism for a liquid dispensing device which provides a positive, instantaneous pressure cutoff whenever the liquid pressurizing piston reaches the end of its delivery stroke.

A more specific object is to provide an improved liquid spraying device of the type disclosed in my aforemen tioned co-pending application incorporating a pressure cutoff release port which cooperates with a variable resistance cylinder and piston structure to function automatically to maintain a more uniform pressure delivery from the pump chamber to the spray nozzle throughout substantially the entire working stroke of the piston.

Other objects as well as the features and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawing wherein:

FIG. 1 is a vertical center section illustrating a hand pressurized liquid spraying device incorporating a uniform pressure liquid pressurizing piston pump structure in accordance with the present invention, the piston being shown at about its midstroke position.

FIG. 2 is an enlarged fragmentary vertical sectional view along the axis of the device illustrating a portion of the structure shown in FIG. 1 but with the piston shown at the end of its liquid pressurizing and delivery stroke.

FIG. 3 is a horizontal section taken on the line 3-3 of FIG. 2.

FIG. 4 is a still further enlarged fragmentary elevational view looking outwardly from the center of the pump chamber toward the chamber inlet-outlet port illustrating the piston O-ring seal (divorced from the piston) in the same position in which it is illustrated in FIG. 2.

Referring in more detail to the drawings, FIG. 1 illustrates a preferred example of a uniform pressure liquid delivery structure in accordance with my present invention applied to a liquid spraying device 10 such as that disclosed and claimed in my aforesaid co-pending application Ser. No. 712,306, filed Mar. 11, 1968, to which reference may be had for a more detailed disclosure of the structure and operation of liquid spraying device.

Briefly, device 10 comprises a manually operated, handheld liquid spraying device which includes a non-pressurized, refillable container 12, for holding a supply of the liquid to be dispensed, the open upper end of which 1s closed by a screw-on cover structure 14. Device 10 also includes a manually actuated, spring pressurized pump comprising a piston 16 reciprocable in a cylinder 18. In the embodiment illustrated herein, cylinder 18 is an integral part of cover 14, whereas piston -16 is connected by rigid stem 20 to a spray head 22 which is slidable guided on the container 12 by a dependent skirt 24 which also forms a hand hold for the device. Spray device 10 is cocked for spraying by pushing spray head 22 downwardly so that it telescopes onto container 12, preferably while the container is supported as by resting it on a firm surface such as a table top. This movement drives piston 16 down on its suction stroke against the force of a yieldable coil spring 26, causing liquid to be drawn from the body of liquid 28 in container 12, up dip tube 30, past inlet check valve 32 into the pump chamber 34. Chamber 34 is axially defined between piston 16 and the fixed upper end wall 36 of chamber 34 which is formed by a piston retainer and plug insert 38 secured by rivets 40 to a screw top part 42 of closure 14. This downward movement of piston 16 also simultaneously cocks spring 26 to its fully stressed condition. The liquid trapped under high pressure in pump chamber 34 is then releasable at will in the form of a spray 44 by the operator depressing a spray button 46 which opens a normally closed discharge valve 48 of the device. Valve 48 is preferably constructed in accordance with my U.S. Pat. No. 3,396,874.

When it is desired to refill container 12 with liquid, spray head 22 is rotated relative to container 12 to thereby unscrew closure -14 from the container, closure 14 being keyed to head 22 by a key 50 which projects into a keyway 52 in skirt 24.

Referring in more detail to FIGS. 2 and 3, it will be seen that inlet check ball 32 seats in a cup-like valve body 54 and closes an inlet port 56 which communicates with the upper end of dip tube 30. Valve body 54 and dip tube 30 are both seated by press fits in a lateral protuberance 58 joined integrally to one side of cylinder 18 as best seen in FIGS. 1 and 3. The space above check ball 32 forms a valve chamber 59 closed at its upper end by insert 38. A flexible tube 60 extends in sealed relation through insert 38 to connect chamber 59 with valve '48. A short passage 62 extends radially of cylinder 18 between the upper end of pump chamber 34 and valve chamber 59 to form a combined inlet-outlet for pump chamber 34.

In accordance with a principal feature of the present invention, cylinder 18 is provided with an escape port or release passage adapted to connect pump chamber 34 with a zone of pressure lower than that existent in the pump chamber when piston 16 is almost at the end of its up stroke, which constitutes the fluid pressurizing or delivery stroke of the piston. In the preferred embodiment disclosed herein, this escape port constitutes a tapering groove 64 best seen in FIGS. 2, 3, and 4 which is machined or molded into the cylindrical interior wall 66 of cylinder 18 immediately below passage 62. Groove 64 tapers to a point 68 at its lower end and the axis of the groove is inclined outwardly towards passage 62. Preferably the'upper end of groove 64 intersects with a radially extending groove 70 which forms passage 62. Groove 70 is cut or molded into the flat bottom wall 71 of a notch 72 (FIG. 4) in closure 42 which receives a keying and locating projection 73 of insert 38. Groove 70 has a semicircular cross sectional configuration, groove 70 being covered by projection 73. The lower end 68 of groove 64 blends smoothly into the cylinder wall 66 at a point just below rubber O-ring '74 when at its uppermost position as shown in FIGS. 2, 3, and 4. O-ring 74 serves as the liquid sealing element for bore 66, and is carried between a flange 76 of piston 16 and a flange 78 of stem 20, these parts together forming the piston.

The starting depth of the groove 64 at its upper end will vary depending upon the relative size of the cylinder 18, pump chamber 34, piston stroke length, etc., but in the particular embodiment disclosed herein wherein the inside diameter of bore 66 is approximately .5 inch, the length of the piston stroke is approximately .75 inch and the parts are constructed by being scaled from the drawings herein utilizing these dimensions, the depth of groove 64 at its upper end measured radially of cylinder 18 from the center of the groove to an imaginary extension of wall 66 is in the range of about .018 to .025 inch. The inclination of groove '64 relative to the axis of cylinder 18 is approximately degrees. The diametrical thickness of O-ring 74 should be about .070 inch in its free state condition. It is to be understood that O-ring 74 is assembled between flanges 76 and 78 under axial compression with a slight squeeze so that it is distorted radially outwardly into liquid sealing engagement with wall 66. O- ring and its piston groove are thus dimensioned relative to the diameter of bore 66 to produce a squeeze factor such that the O-ring is under compression radially by wall 66 throughout the working stroke of piston 16.

It is to be understood that the spring chamber 79 formed within cylinder 18 below the piston in which spring 26 is housed is in communication with the interor of container 12 through an opening 80 in the bottom of cylinder 18. Hence fluid pressure in chamber 79 is the same as that of the head space 82 of container 12, which in turn is maintained substantially at atmospheric pressure through a venting arrangement such as those disclosed in my aforementioned co-pending application Ser. No. 712,306 or in my co-pending application entitled Leak Proof Container Seal, Ser. No. 779,755 filed Nov. 29, 1968.

In operation, when piston 16 is travelling upwardly from the lower limit of its travel, which corresponds to the beginning of its liquid delivery or pressurizing stroke or the end of its intake stroke (indicated in broken lines in FIG. 1), until seal 74 starts to uncover lower end 68 of groove 64, seal 74 maintains a liquid tight seal with wall 66 which prevents escape of the liquid under pressure from pump chamber 34 downwardly past piston 16 to the zone of lower pressure comprising the chamber 79.

During this major portion of the up stroke of the piston, which is governed by release of the liquid trapped in chamber 34 by finger operation of spray button 46, the liquid is delivered at a substantially uniform pressure to the spray nozzle 83 in spray button 46 and hence a good quality spray 44 is produced by hydraulic atomization in the nozzle. Then just as piston 16 is almost at the top of cylinder -18 and thus is within say .06 inch of the end of its travel on the top stroke, O-ring 74 slides past the lower end 68 of groove 64, thereby opening up a bypass passage (relative to spray nozzle 83) for the liquid under pressure to escape from chamber 34, and from the communicating passageways 62, 59 and 60, downwardly between the O-ring and groove 64 to the radial clearance space normally provided between flange 76 and wall 66. This clearance space in turn is in wide open communication via chamber 79 with head space 82, assuming that the level of the liquid in the container is below opening 80. Even if the liquid is above this opening, the pressure of the air trapped in chamber 79 is only very slightly above atmospheric and hence much lower than the pressure seen by the liquid at the inlet to spray nozzle 83.

When the bypass port 64 is thus opened just prior to piston 16 reaching the end of its up stroke, the liquid and/0r liquid-air mixture, which amounts to only a drop or two, still remaining under pressure in pump chamber 34 squirts through the escape port 64, thereby suddently relieving pressure in chamber 34 and allowing piston 16 to ram home in the last fraction of an inch of its up stroke. This completely empties chamber 34 and causes a very sudden and severe drop in the liquid pressure in passage 62 and valve cavity 59, say from p.s.i. to substantially atmospheric. Hence the pressure exerted on the liquid at the inlet to nozzle 83, which has been constant up to the aforementioned escape port opening action, is suddenly ended abruptly and a dramatic instantaneous cut-off of the spray mist 44 results. This in turn has been found to successfully eliminate the annoying nozzle spitting as the last of the liquid in chamber 34 is being dispensed and the contents of chamber 34 are about to be exhausted, and believed to be caused by an end-of-stroke gradual pressure drop due to small bodies of air retained in the pockets of the structure forming the passageways 62, 58, 60 and valve 48.

As soon as the pump chamber pressure has been relieved by opening of escape port 64 as described above, the escape port will be automatically closed by O-ring 74 expanding radially outwardly into groove 64 in response to the pressure relief. Due to its resiliency O-ring 74 deforms and flows or protrudes into groove 64, forming a protuberance 84 (as best seen in FIG. 3) which is effective to re-seal groove 64 under these low pressure conditions. Thus when spray head 22 is pushed down to recock the spray device 10 and thereby draw liquid from container 12 up dip tube 30 into pump chamber 34, the suction created by the expanding volume of chamber 34 cannot draw air from spring chamber 79 through passage 64 into pump chamber 34 even during the time that O-ring 74 is travelling from its uppermost position (FIGS. 2 and 4) until it has passed downwardly beyond the lower end 68 of groove 64. Hence O-ring 74 acts as an automatic valve which insures that air does not become entrained in the liquid pressurizing conduits and chambers of the device as a result of the provision of the pressure relief of escape port 64.

In accordance with another feature of the present invention, more uniform liquid delivery pressure is obtained throughout the working stroke of piston 16 by forming the bore 66 of cylinder 18 throughout the portion thereof engaged by O-ring 74, and preferably the entire cylinder from its extreme upper end down to opening 80, with a frusto-conical configuration so that the wall of bore 66 converges downwardly and diverges upwardly with a slight taper. Preferably this taper is approximately on the order of /2 in a working embodiment of my invention constructed according to the forementioned dimensions when scaled from the drawing to these dimensions.

The tapered cylinder bore 66 cooperates with the resilient O-ring 74 to help compensate for the variation in liquid pressurizing force developed by coil spring 26 when, for reasons of economy, the same is a variable rate spring and hence exerts a higher force when fully stressed than when expanded. Due to the taper of bore 66 the greatest radial compnession or squeeze is applied to seal 74 when piston 16 is at the lower limit of itsstroke. Therefore the frictional drag of the seal 74 along wall 66 will be greatest during the first portion of the upward travel of piston 16 on its delivery stroke. As the piston moves upwardly, the gradually increasing diameter of bore 66 causes a gradual reduction in the unit pressure engagement force of O-ring 74 with bore 66, thereby reducing the drag resistance of the O-ring simultaneously with the drop-off in force exerted by spring 26 as it expands in driving piston 16 upwardly. Thus the pressure developed in the liquid in pump chamber 34 is maintained more uniform throughout the working stroke of the piston, with the end-of-stroke pressure being very sharply cut-off when the pressure relief bypass port 64 is opened as described above.

The tapered cylinder bore is also advantageous in that it permits much easier and positive molding of cylinder 18 when the parts are injection molded from plastic material, which is the preferred method of manufacture employed in making my liquid spraying device 10.

From the foregoing description it will now be apparent that my invention provides a liquid pressurizing structure which can be incorporated into spray-type liquid dispensing devices without the need for any added parts, by very simple and low cost manufacturing operatlons and which will reliably function to automatically overcome the problems created by gradual end-of-stroke pressure drop-01f and will operate to maintain a more constant hydraulic pressure in such devices or systems.

I claim:

1. In a liquid spraying device having a container adapted to hold a quantity of liquid including a receptacle having an opening for filling the same with the liquid and a cover adapted to removably close said liquid fill opening and to define with said receptacle a head space above the body of liquid in the receptacle, a spray pressurizing head movably mounted on said container including first and second pump members movable relative to one another and defining a liquid pressurizing chamber and operably connected to said cover and head such that movement of said head relative to said cover changes the volume of said chamber, an inlet conduit adapted to conduct pressurized liquid from said chamber to said spray nozzle, a discharge valve in said outlet conduit, and biasing means operably connected to said pump members to bias said pump members in a direction tending to decrease the volume of said chamber whereby said biasing means is stressed when said device is manually actuated to move said head relative to said receptacle to thereby draw liquid from said receptacle into said chamber, the improvement comprising a pressure relief passageway having one end communicating with said pump chamber, said passageway having another end communicating with a zone of pressure lower than that in said pump chamber at least when said pump members are positioned relative to one another to produce almost the minimum volume of said pump chamber, and means controlling flow of liquid through said passageway responsive to the position of said pump members to open communication between said pump chamber and said zone of lower pressure via said passageway only when said pump members are between said almost minimum volume relative position and said minimum volume relative position to thereby suddenly relieve the pressure in said pump chamber and outlet conduit as said pump members are moving toward said minimum volume relative position.

2. The combination set forth in claim 1 wherein said device has means for maintaining the pressure in said head space about at atmospheric pressure, wherein said pump members comprise a cylinder and a piston reciprocable in said cylinder, and wherein said one end of said pressure relief passageway opens to said outlet conduit and said other end of said passageway opens to the interior surface of the wall of said cylinder, said piston having sealing means in liquid sealing engagement with the wall of said cylinder, said zone of lower pressure comprising at least a space communicating with the liquid in said receptacle and the side of said piston remote from said pump chamber, said other end of said passageway being located relative to the travel of said sealing means such that said sealing means moves past said other end of said passageway when said piston reaches said pressure relief position thereof. to thereby connect said pump chamber via said outlet conduit and said passageway with said low pressure space of said cylinder.

3. The combination set forth in claim 2 wherein said biasing means comprises a spring.

4. The combination set forth in claim 3 wherein said spring comprises a variable rate compression coil spring located in said low pressure space in said cylinder.

5. The combination set forth in claim 3 wherein at least the portion of said cylinder wall engaged by said piston sealing means throughout the travel thereof with said piston has a gradually tapering diameter which increases in the direction of travel of said piston which tends to decrease said pump chamber volume to thereby provide a gradual reduction in the frictional drag of said sealing means along said cylinder wall as said spring moves said piston in the direction tending to decrease the volume of said pump chamber.

6. The combination set forth in claim 5 wherein said piston sealing means comprises a resilient annular sealing member carried by said piston and radially compressed by the sliding engagement thereof with said cylinder wall, and wherein said pressure relief passageway comprises a shallow groove in the wall of said cylinder, said resilient seal expanding into said shallow groove to reseal the same in response to release of liquid from said pump chamber reducing the pressure therein substantially to that of said zone of lower pressure.

7. In a liquid pressurizing device having a cylinder and a piston in said cylinder and reciprocable relative to one another to define a variable volume pump chamber, said piston carrying sealing means in sliding sealing engagement with the wall of said cylinder, the combination therewith of means for producing a sudden pressure drop in said pump chamber when said piston and cylinder are relatively positioned at a pressure relief position wherein said pump chamber volume is reduced almost to its mini mum, said means comprising a bypass passageway having an outlet port communicating with said cylinder at a point disposed on the side of said sealing means of said piston remote from said pump chamber only when said piston and cylinder are positioned between said pressure relief position thereof and their position at the minimum volume condition of said chamber, said passageway having an inlet port in communication with said pump chamber throughout the travel of said piston and said cylinder relative to one another.

8. The combination set forth in claim 7 wherein said device contains a spring urging said piston and cylinder toward their minimum chamber volume position, and wherein at least the portion of said cylinder wall engaged by said piston sealing means throughout the travel thereof with said piston has a gradually tapering diameter which increases in the direction of travel of said piston which tends to decrease said pump chamber volume to thereby provide a gradual reduction-in the frictional drag of said sealing means along said cylinder wall as said spring moves said piston in the direction tending to decrease the volume of said pump chamber.

9 The combination set forth in claim 8 wherein said piston sealing means comprises a resilient annular sealing member carried by said piston and radially compressed by the sliding engagement thereof with said cylinder wall, and wherein said pressure relief passageway comprises a shallow groove in the wall of said cylinder, said resilient seal expanding into said shallow groove to reseal the same in response to release of liquid from said pump chamber reducing the pressure therein substantially to that of said zone of lower pressure.

10. In a liquid spraying device having a container adapted to hold a quantity of liquid including a receptacle having an opening for filling the same with the liquid and a cover adapted to removably close said liquid fill opening and to define with said receptacle a head space above the body of liquid in the receptacle, a spray pressurizing head movably mounted on said container including first and second pump members movable relative one to one another and defining a liquid pressurizing chamber and operably connected to said container and head such that movement of said head relative to said container varies the volume of said chamber, an inlet conduit adapted to conduct liquid in the receptacle to said chamber, a spray nozzle, an outlet conduit adapted to conduct pressurized liquid from said chamber to said spray nozzle, a discharge valve in said outlet conduit, and a variable rate spring operably connected to said pump members to bias said pump members in the direction tending to decrease the volume of said chamber whereby the stress applied to said spring is increased when said device is manually actuated to move said head relative to said container for drawing liquid from said receptacle into said pump chamber, the improvement wherein said pump members comprise a cylinder and a piston reciprocable in said cylinder, said piston having resilient seal means slidably engaging the wall of said cylinder to prevent escape of liquid under pressure from said pump chamber, said cylinder having a slight frusto-conical configuration tapering so as to increase in internal diameter in the direction of movement of said piston tending to decrease the volume of said pump chamber to thereby produce a gradual decrease in the frictional drag of said seal means along said cylinder wall as said spring moves said piston in the direction tending to decrease the volume of said pump chamber.

References Cited UNITED STATES PATENTS 1,865,914 7/1932 Jaden 222-321 X 2,505,198 4/1950 Moskowitz et al. 103216 X 2,568,057 9/1951 Cotter 222-385 X 2,878,974 3/1959 Dobkin 222385 X 3,130,675 4/1964 Cripe 103-41 X 3,116,855 1/1964 Thomson 222340 X SAMUEL COLEMAN, Primary Examiner N. L. STACK, 1a., Assistant Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE 9 CERTIFICATE OF CORRECTION Patent No. 3 ,5l4,0l7 Dated May 26, 1970 Inventor(s) CARL E. MALONE It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5, line 72, cancel "inlet" and insert outlet- Signed and sealed this 9th day of May 1972.

(SEAL) Attes'i:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Atbesting Officer Commissioner of Patents 

